Why did the united states ultimately decide to drop an atomic bomb on japan?

It was the only way to get the Japanese to stop fighting. The people who argue against the use of bombs seem to have no idea of the circumstances of their use and no idea of what the alternatives were. Apparently, people who take this position don't understand that we were attacked by Japan. We didn't attack them. They attacked us! We didn't start it, they did. And the only way to stop them from killing was to drop bombs.